grimlord I had the same sort of thing happen a few years ago but during the winter. This is going to sound ridiculous but it was an orange coloured slime and it was on the grass and didn't go away for a few days - only to reappear again in a different place like you say - overnight! Honestly I am not taking the mick, it really stumped me and I was afraid to tell anyone in case they thought I'd lost the plot! Sorry I can't enlighten you as to what it is, but I'd love to here if you find out any more!